---
name: "eventfd_signal"
section: "9"
platform: "linux"
package: "linux-manual-4.9"
version: "4.9.228-1"
release: "Debian 9 (Stretch)"
platforms: ["linux"]
url: "https://new.carta.tech/eventfd_signal"
---

# eventfd\_signal(9)

Adds n to the eventfd counter.

## NAME

eventfd\_signal - Adds *n* to the eventfd counter.

## SYNOPSIS

**\_\_u64 eventfd\_signal(struct eventfd\_ctx \*** *ctx***, \_\_u64** *n***);**

## ARGUMENTS

*ctx*

\[in\] Pointer to the eventfd context.

*n*

\[in\] Value of the counter to be added to the eventfd internal counter. The value cannot be negative.

## DESCRIPTION

This function is supposed to be called by the kernel in paths that do not allow sleeping. In this function we allow the counter to reach the ULLONG\_MAX value, and we signal this as overflow condition by returning a POLLERR to [poll(2)](/poll/2.md).

Returns the amount by which the counter was incremented. This will be less than *n* if the counter has overflowed.

## COPYRIGHT